Hi, I'm new to the forum and looking for help. I am trying to make a homemade bug zapper using a 15kv 30ma neon sign transformer.
I have a store bought one but it's too small to do the job on a bell hornet problem I have. At night, they come around the other to gobble up the mosquitos and other bugs but are too big to get into the grid. My wife has been stung by one and it wasn't pretty. anyway, my first attempt was to use a wire grid similar to the store bought ones, but making the holes large enough for a hornet that size to enter. Problem was it kept arcing to itself everytime I turned it on. I had to make the distance between the two grids about 3" to stop that but now it's too far apart for the critter to draw and arc when it enters. So I scrapped that idea and have set up a system using 3/16 brass rods spaced about 1 1/2" apart. It doesn't arc on power up, but when a bug enters and the arc starts, it won't stop!! I'm new to this kind of electrical frontier but I have been in electronics for about 30yrs as a technician. Just no experience with HV low current and air gaps. Is my transformer just too big for the job? I feel like I'm missing something here and just can't wrap my brain around it. How can I get this thing to zap and then stop the arc when the job is done? Thanks in advance.
PS it does make an awesome Jacob's Ladder though!!

Yes I understand this. A friend of mine has a homemade one using a transformer from an old steam jenny that is 10kv @ 23ma and it will knock the hornet to the ground but sometimes they fly off mad I guess, sometimes they will be so mad they fly right back into the thing only to be knocked right back down. I thought a 15kv might just do the trick. I just can't get that arc to stop once it starts.

Yeah, have you ever seen one of these things. They are almost as big as a small hummingbird!! We are really plagued with them. If we go out after dark and turn on any lights, which attracts the smaller things like moths, mosquitoes and what not, these things show up in numbers looking for a meal. Quite a nusiance if not a threat!! Our dog even goes nuts when they are around.

Anyway, I'm wondering if there's not a way to shunt this arc once the initial spark has done it's job? This air gap thing has got me confused. I think my store bought bug zapper is around 2kv and the air gap there is about 1/4". So does this mean with 15kv I should be looking at around 2" or so? I'm sure there's a HV technician out there who can help me out.

Hey thanks for the reply. I have seen those same circuits and may ending up trying them. But are you saying that 15kv @ 30ma isn't enough? I mean this thing will through a scary arc 2 1/2 to 3 inches and you can smell the ozone in the air. I would think it is plenty. Maybe too much!

Hey thanks for the reply. I have seen those same circuits and may ending up trying them. But are you saying that 15kv @ 30ma isn't enough? I mean this thing will through a scary arc 2 1/2 to 3 inches and you can smell the ozone in the air. I would think it is plenty. Maybe too much!

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Here you go:

How It Works: The yellow jackets love fish and will begin to cut off small pieces to take back to the nest. In their "excitement" of buzzing around the bait a few will occasionally hit the water. The soap in the water breaks the surface tension of the waterproof coating on the yellow jacket and it instantly sinks in the water and drowns in a few seconds. Some yellow jackets will successfully haul a piece of meat back to the nest and tell all the other gatherers in the nest where this great food source is. Soon all the wasps from the nest will be working on this fish and over a period of time, all will eventually make mistakes and either fall off the fish and into the water or bump other wasps flying around and knock themselves in the drink, then its curtains for them too. It only takes a day or two to wipe out nearly every yellow jacket in your area.

I was a welder in my previous life, and the high voltage ang high freq. we could make arc to our hands didn't hurt a bit. But if you touched the ground, you were dead. i cant vouch that the current is the culprit, but if your already above the voltage, current is what's left.

Thanks for the fish and soapy water idea, but I'm not so sure bell hornets would be attracted to that. They seem to like to come around at night when we are sitting out. Any light source that attracts smaller critters brings the BIG hornets out in force.
Can I use this NST as a powersource for a circuit that maybe steps up the voltage even more without the current? I know, I'm headed for the Tesla Coil thing. sorry, seems like the older I get the more I forget!!!

I think that the problem is in the current. I´m not a biologist, but I think these suckers need a lot more current to kill than a human, maybe because of the crust they have. I would try some microwave transformer, which has about 2kV and up to 500mA, depending on the microwave. This should be the right mix to kill them.
But be sure you don´t short the wires, these power levels available are quite large and dangerous.

You're on the right track, tho' it is a fair balancing act to get the right ratio of volts-to-Milliamps. The large "Ohmite" ceramic rheostats on a control board allow you to balance your output.

What is the design of your trap ?? I have used standard hexagonal "chicken wire" for larger critters.................having built several of these for farm applications.

Part of the trick, is designing your trap so that gravity can remove the corpses from it. The other part is making sure your new toy isn't causing gross noise on your neighbors' radio or teevee..........

Lastly........hang the thing where idiots can only watch, and cannot toss captured victims into the grid to watch them fry

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No one will be near it.
I used hardware cloth, or rat wire with 1/2" grids and had to make it so far apart to keep from arcing to itself that a bug wouldn't trip it.
I'm now using 3/16" brass rod's spaced about 1 1/2" apart with no self arcing but if an arc starts, it won't stop.

Who cares about the neighbor's radio?? Just kidding. I know it's broadband RF but haven't seen any interference with my stuff yet. Buy the way, I'm an "old" electronic warfare tech. No jamming so far!!

Lessee, seems to me that the "rule of thumb" is 3kv per mm; that is, it takes 3kv to start an arc across a dry air gap of 1mm.

However, once the arc starts, the air is ionized and so it doesn't take as much voltage to keep the arc going.

You really need less voltage and more current. The lower voltage won't be able to maintain the ionization of the air without a moisture-containing bug between the grids. The higher current will zap the dickens out of the bug, frying the moisture out of it in a big hurry.

A multiplier feeding a capacitor bank large enough to positively take out a bug might do the trick, since thecaps will then be more or less discharged from the zap (quencing the arc) and will have to be recharged to take out another hornet.

Thanks for the fish and soapy water idea, but I'm not so sure bell hornets would be attracted to that. They seem to like to come around at night when we are sitting out. Any light source that attracts smaller critters brings the BIG hornets out in force.
Can I use this NST as a powersource for a circuit that maybe steps up the voltage even more without the current? I know, I'm headed for the Tesla Coil thing. sorry, seems like the older I get the more I forget!!!

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You could rebuild your existing zapper with an old microwave oven transformer and it's associated voltage doubler diode/cap... The output is typically around -2kVDC @ several hundred milliamps. That ought to be enough to vaporize the little monsters!

If you're thinking of building a Tesla Coil with that NST, the attached excel spreadsheet will come in handy!